List of sources:
Cape of Good Hope. Report of the committee of the Albany Museum, 1890.
Dictionary of South African biography (article on Henry Barkly), Vol. 2, 1972.
Gunn, M. & Codd, L.E. Botanical exploration of southern Africa. Cape Town: Balkema, 1981.
Kerkham, A.S. Southern African botanical literature, 1600-1988. Cape Town: South African Library, 1988.
Schoeman, K. Sir Henry and the Stapeliae. Quarterly Bulletin of the South African Library, 1998, Vol. 52, No. 4, pp. 132-133.